Wireless channel sounder with fast measurement speed and wide dynamic range

ABSTRACT

An example device includes antennas to receive wireless signals from a wireless transmitter and to output radio frequency signals based upon the wireless signals that are received, low noise amplifiers coupled to the antennas to amplify the radio frequency signals, and a receiver stage to generate, based upon the radio frequency signals, digital representations of the wireless signals that are received via the antennas and to determine a measure a wireless channel parameter from the digital representations of the wireless signals.

This application is a continuation of U.S. patent application Ser. No.15/293,995, filed Oct. 14, 2016, now U.S. Pat. No. 10,397,811, which isherein incorporated by reference in its entirety.

The present disclosure relates generally to wireless channelmeasurements, and more particularly to devices, non-transitory computerreadable media, and methods for determining measures of wireless channelparameters.

BACKGROUND

A wireless channel sounder is a device for measuring wireless channelrelated parameters such as complex impulse response, path loss, receivedsignal strength (RSS), excess delay, or root-mean-square (RMS) delayspread, Doppler spread, fade rate, angle of arrival (AoA) and/or angleof departure (AoD), and the like as experienced by a user equipment orbase station. In one implementation, a wireless channel sounder mayutilize a directional antenna. For instance, to measure AoA using adirectional antenna, the antenna may be turned in incremental steps tomeasure the RSS. The AoA is recorded where the RSS is at a maximum.While this solution is inexpensive, it is a relatively slow measurementtechnique.

SUMMARY

In one example, the present disclosure discloses a device fordetermining measures of wireless channel parameters. For example, thedevice may include antennas to receive wireless signals from a wirelesstransmitter and to output radio frequency signals based upon thewireless signals that are received, low noise amplifiers coupled to theantennas to amplify the radio frequency signals, and a receiver stage togenerate, based upon the radio frequency signals, digitalrepresentations of the wireless signals that are received via theantennas and to determine a measure of a wireless channel parameter fromthe digital representations of the wireless signals.

In another example, the present disclosure discloses a device,computer-readable medium, and method for determining measures ofwireless channel parameters. For example, a processor may activate afirst plurality of low noise amplifiers that is coupled to a firstplurality of antennas, receive a first plurality of wireless signals viathe first plurality of antennas and the first plurality of low noiseamplifiers, and determine a first measure of a wireless channelparameter based upon the first plurality of wireless signals that isreceived. The processor may further deactivate the first plurality oflow noise amplifiers, activate a second plurality of low noiseamplifiers that is coupled to a second plurality of antennas, receive asecond plurality of wireless signals via the second plurality ofantennas and the second plurality of low noise amplifiers, and determinea second measure of the wireless channel parameter based upon the secondplurality of wireless signals that is received.

BRIEF DESCRIPTION OF THE DRAWINGS

The teachings of the present disclosure can be readily understood byconsidering the following detailed description in conjunction with theaccompanying drawings, in which:

FIG. 1 illustrates a block diagram of an example device, e.g., awireless channel sounder, in accordance with the present disclosure;

FIG. 2 illustrates a block diagram of a portion of an example device,e.g., a wireless channel sounder, in accordance with the presentdisclosure;

FIG. 3 illustrates a perspective view of an example device, e.g., awireless channel sounder, in accordance with the present disclosure;

FIG. 4 illustrates a flowchart of an example method for determiningmeasures of wireless channel parameters; and

FIG. 5 illustrates an example high-level block diagram of a computingdevice specifically programmed to perform the steps, functions, blocks,and/or operations described herein.

To facilitate understanding, similar reference numerals have been used,where possible, to designate elements that are common to the figures.

DETAILED DESCRIPTION

The present disclosure broadly discloses methods, computer-readablemedia, and devices for determining measures of wireless channelparameters. In particular, examples of the present disclosure describewireless channel sounders with fast measurement speeds, low noisefigures, and improved receiver sensitivities and dynamic ranges overwhich the wireless channel sounders can correctly measure andcharacterize the wireless channel parameters operating in any frequencyspectrum.

In general, a wireless channel sounder is a device for measuringwireless channel related parameters such as a complex impulse responseof the wireless channel, a path loss, an excess delay, aroot-mean-square (RMS) delay spread, a Doppler spread, a fade rate, anangle of arrival (AoA) or angle of departure (AoD), and the like asexperienced by a user equipment or base station. In addition, themeasurements of the wireless channel related parameters under a varietyof test conditions enables the modeling of the behavior for thesechannel parameters under different scenarios and conditions, as well asthe simulation and prediction of the performance of a base station or auser equipment under such scenarios and conditions. In one example, awireless channel sounder of the present disclosure comprises aswitched-antenna array with low noise amplifiers (LNAs) coupled to theantennas, or antenna elements, of the switched-antenna array. In oneexample, the LNAs are used for antenna switching. For instance, toselect and de-select antennas, a LNA associated with an antenna isturned on and off using a biasing circuit. In addition, in one example,antenna elements and LNAs are grouped into sectors, e.g., into antennasector units, with antenna sector units arranged to cover 360 degrees inazimuth. In one example, 360 degree coverage is provided by eight 45degree (e.g., at half-power beamwidth) antenna sector units. In oneexample, antenna sector units may be arranged into two levels, eachcovering 45 degrees in elevation, e.g., from −22.5 degrees below horizonto 22.5 degrees above horizon, and from 22.5 degrees above horizon to67.5 degrees above horizon, for a total of 16 sector units. In oneexample, each antenna sector unit may comprise four antennas which maybe simultaneously connected to four receivers via a bank of switchingLNAs.

In other solutions, wireless channel measurements may be performed usinga directional antenna. For instance, to measure AoA using a directionalantenna, the antenna may be turned in incremental steps to measure thereceived signal strength (RSS). The AoA is recorded where the RSS ismaximum. While this solution is inexpensive, it is a relatively slowmeasurement technique. For example, it may take hundreds of seconds totens of minutes to complete one set of measurements covering 360 degreesin azimuth and 90 degrees in elevation at one particular location awayfrom the transmitter. In contrast, examples of the present disclosuremay determine the AoA by calculating a phase difference between wirelesstest signals received at antenna elements at different positions withinthe array, and mapping the phase difference(s) to the incident directionof the wireless test signals. Since the phase of a received signal isgenerally more stable than the received signal strength (RSS), AoAestimation using phase difference calculations can achieve higheraccuracy than RSS-based localization approaches. An antenna sector unithaving an array with as few as two antenna elements may suffice tomeasure AoA with moderate accuracy, e.g., up to and including one degreeor better accuracy, in either azimuth or elevation. An antenna sectorunit with an array of four antenna elements, e.g., arranged in a quadarray, may achieve accurate AoA measurements with respect to bothazimuth and elevation.

In addition, AoA measurements for a single location may be gathered inas few as 140-175 milliseconds. For example, with a reference clock of768 MHz and a wireless test signal of 2048 symbols, the acquisition timeper four antennas/antenna ports per antenna sector unit may be 2.7microseconds ( 1/768 MHz×2048). To increase the performance of thewireless channel sounder, multiple snapshots may be taken per antennasector, e.g., 32 snapshots, for an acquisition time per sector of 86microseconds for 32 snapshots. The total acquisition time of 16 sectorsmay be approximately 2.6 milliseconds, e.g., with an estimate of 75microseconds per sector for switching LNAs, waiting for LNAs to settleprior to collecting data, etc. For instance, the acquisition time overall sectors may be calculated as (85 microseconds+75 microseconds)*16sectors=2.6 milliseconds. In addition, since measurements may be takenat all sectors/antenna sector units for wireless test signals frommultiple transmit antennas having different orientations (e.g., sevenantennas), the acquisition time across all multiple input multipleoutput (MIMO) positions may be (2.6 milliseconds+20 millisecondsestimated for housekeeping)×7 sectors=140 to 175 milliseconds.

Examples of the present disclosure also improve the overall dynamicrange a wireless channel sounder as compared to prior solutions that usePIN (p-type region, intrinsic region, n-type region) diode or mechanicalswitches for antenna switching. For example, low-noise amplifiers (LNAs)are as fast as solid state switches but with significant gain, e.g., 16dB or more, as compared to an 8-13 dB insertion loss for a solid stateswitch, such as a PIN diode switch. For example, a maximum allowablenoise at a wireless channel sounder antenna of the present disclosuremay be −138 dBm, taking into account thermal noise of −84 dBm/1 GHz, anoise figure of 5 dB, averaging gain of 15 dB, a processing gain of 33dB and an antenna gain of 11 dBi (e.g., gain relative to isotropicradiator) when LNAs are attached directly to the antennas. In oneexample, the dynamic range may be 173 dB or better, e.g., assuming for atotal effective radiated power of the transmitter (Pt ERP) of 45 dBm anda desired signal to noise ratio (SNR) of 10 dB. This corresponds tocommunication distances greater than 200 meters in a millimeter wavesystem. In addition, an overall noise profile of approximately 4 dB isachievable in a wireless channel sounder according to the presentdisclosure. It should also be noted that microelectromechanical switches(MEMS) may be used in an alternative wireless channel sounder design.However, while MEMS have a lower insertion loss as compared to a PINdiode or other solid state switches, MEMS are relatively slow to switch.

Although examples of the present disclosure are applicable to a widerange of frequency bands, in one example, wireless channel sounders ofthe present disclosure may relate to centimeter and millimeter wavesystems. Due to propagation characteristics of millimeter wavefrequencies, the antenna apertures at high frequency are generallylarger to achieve sufficient gain. In particular, the gain of antennasis inversely proportional to the wavelength or directly proportional tothe center frequency of operation. Antenna switches operating at thesefrequencies are physically large, lossy, and may provide approximately40 dB isolation between output ports. In contrast, examples of thepresent disclosure use biasing circuits to turn LNAs on and off toselect associated antennas/antenna elements. In this way, the noisefigure of the receiver is reduced as compared to a millimeter waveswitch (e.g., each antenna is directly connected to an LNA, rather thanto a switch). In addition, the isolation between adjacent sector'santennas (e.g., the cross interference) may be 80 dB or more, asexperienced by the receivers. For instance, when an LNA is in the offposition, little to no signal will be passed through the LNA.

It should be noted that for illustrative purposes, various wirelesschannel sounder systems are described herein in connection withparticular quantities or values. However, wireless channel soundersystems of the present disclosure may include different quantities ofvarious components, and/or operating parameters which may have anynumber of different values. For instance, a wireless channel soundersystem may have a different number transmit antennas, may have antennaswith different beamwidths, may utilize different frequencies, mayutilize different transmit powers, and so forth. In addition, a wirelesschannel sounder system may include a different number of antenna sectorunits covering a same or a different range in azimuth and/or elevation,may have sectors with different coverages, may have a different numberof antenna elements per sector, may have a different desired SNRs, mayutilize a fewer number of samples per antenna for a different averaginggain, and so forth. These and other aspects of the present disclosureare discussed in greater detail below in connection with the examples ofFIGS. 1-5.

To aid in understanding the present disclosure, FIG. 1 illustrates anexample device 100, e.g., a wireless channel sounder, in accordance withthe present disclosure. In one example, the device 100 may be used todetermine measures of various wireless channel parameters. In oneexample, the device 100 may be used to receive wireless test signalsthat are transmitted in an environment, where the wireless test signals,as received, may be used to calculate or determine the measures ofvarious wireless channel parameters such as: multipath amplitude(s),phase(s), direction(s) or angle(s) of arrival, a path loss, an excessdelay, a RMS delay spread, a Doppler spread, a fade rate, a compleximpulse response of the wireless channel, and so forth. In one example,the transmitter may comprise a switched antenna array with transmittingantennas having different orientations, e.g., a curved array. Forinstance, in one example, a switched antenna array to transmit wirelesstest signals may have seven transmitting antennas, each antenna orientedto cover 18.5 degrees of azimuth at half-power beamwidth, which maycover a total of 120 degrees in azimuth (with a small overlap inbeamwidth for adjacent antennas in the array).

In one example, a waveform of the wireless test signals transmitted bythe transmitter may comprise a periodic repetition of Zadoff-Chu (ZC)sequences according to Equation 1:x[n]=e{circumflex over ( )}((jπun{circumflex over( )}2)/L),0≤n≤L−1  Equation 1:where L is the sequence length.

In one example, the transmitter may generate a transmission ofpseudorandom noise (PN) code sequences of a length 1092 corresponding toa processing gain of 30 dB (e.g., 10 log₁₀ L, where L is the sequencelength) according to a reference clock of 768 MHz). In one example, thismay correspond to a 1.4 microsecond sequence block interval. The PN codesequences may be up-converted and amplified (e.g., 20 dB amplification)prior to transmission via one of seven transmit antennas of thetransmitter. In one example, the total effective radiated power of thetransmitter (Pt ERP) may be 45 dBm.

As illustrated in FIG. 1, the device 100 includes a plurality of antennasector units 151-154. Each of the antennas sector units 151-154 mayinclude a plurality of antennas, or an “antenna array,” and a pluralityof low noise amplifiers (LNAs), e.g., four antennas and four LNAs persector. An example antenna sector unit is illustrated in greater detailin FIG. 2 and discussed below. The respective antenna sector units151-154 may be activated and deactivated via control lines 191. Forinstance, timing controller 115 may comprise a biasing circuit, e.g., anapplication specific integrated circuit (ASIC), a field programmablegate array (FPGA), or other type of programmable logic devices that areconfigured to activate and deactivate different ones of the antennasector units 151-154 according to a schedule or otherwise synchronizedto the transmission of wireless test signals.

In one example, the device 100 includes a set 140 of switches 141-144.The switches 141-144 may each comprise a solid state switch, such as aPIN diode switch, an electromechanical or microelectromechanical switch(MEMS), and so forth. In one example, the number of switches correspondsto the number of antennas per sector, or per antenna sector unit. Thus,in the present example, where each of the antenna sector units 151-154includes four antennas, there are four switches 141-144. In addition, asillustrated in the example of FIG. 1, each of the switches 141-144receives an input from an antenna-LNA pair from each of the sector units151-154. In one example, each of the switches may comprise an N×1 switchhaving N input ports and one output port, where N is the number ofsectors, or antenna sector units. Thus, in the present example, switches141-144 may each comprise a 4×1 switch. To illustrate, switch 141receives an input from a first antenna-LNA pair from antenna sector unit151, an input from a first antenna-LNA pair from antenna sector unit152, an input from a first antenna-LNA pair from antenna sector unit153, and an input from a first antenna-LNA pair from antenna sector unit154, switch 142 receives an input from a second antenna-LNA pair fromantenna sector unit 151, an input from a second antenna-LNA pair fromantenna sector unit 152, an input from a second antenna-LNA pair fromantenna sector unit 153, and an input from a second antenna-LNA pairfrom antenna sector unit 154, and similarly with respect to switches 143and 144.

In one example, a timing controller 115 may provide control signals toswitches 141-144 via a control line 192 to control which inputs arepassed to the outputs of the respective switches 141-144. In oneexample, each of the switches 141-144 may receive the same controlsignal. Thus, all of the switches 141-144 may select a similarlypositioned input port to connect to the output port. For instance, afirst control signal from timing controller 115 may cause switches141-144 to pass signals from respective first input ports to therespective output ports of the switches 141-144, while a second controlsignal may cause switches 141-144 to pass signals from respective secondinput ports to the respective output ports of the switches 141-144, andso on. It should also be noted that first input ports of the respectiveswitches 141-144 may each be coupled to antenna-LNA pairs of a sameantenna sector unit, e.g., antenna sector unit 151, while the secondinput ports of the respective switches 141-144 may each be coupled toantenna-LNA pairs of a different antenna sector unit, e.g., antennasector unit 152, and so on. Thus, a control signal from timingcontroller 115 via control line 192 may effectively select signals froma given sector to pass through the set 140 of switches 141-144, whileblocking signals from other sectors.

In one example, the timing controller 115 may synchronize the controlsignals to the set 140 of switches 141-144 via control line 192 with thecontrol signals to the respective antenna sector units 151-154 (whichmay be further synchronized to the timing of the transmission ofwireless test signals from a transmitter). Thus, for example, antennasector unit 151 may be activated via an amplifier control signal via oneof control lines 191, while the switches 141-144 may receive a switchcontrol signal via control line 192 to select respective first inputports that are coupled to antenna-LNA pairs of the antenna sector unit151. Accordingly, the device 100 may receive a first plurality ofwireless test signals via the antennas of antenna sector unit 151, whilethe other antenna sector units 152-154 are deactivated. At another time,the timing control 115 may send a switch control signal to switches141-144 via control line 192 to cause the switches 141-144 to selectrespective second input ports that are coupled to antenna-LNA pairs ofthe antenna sector unit 152. In addition, the antenna sector unit 152may be activated via an amplifier control signal on one of lines 191,while the other antenna sector units 151, 153, and 154 are deactivated.Accordingly, the device 100 may receive a second plurality of wirelesstest signals via the antennas of antenna sector unit 152, while theother antenna sector units 151, 153, and 154 are deactivated. Similarprocedures may be followed to receive a third plurality of wireless testsignals via antenna sector unit 153 and a fourth plurality of wirelesstest signals via antenna sector unit 154. In one example, the timingcontroller 115 may receive configuration instructions, e.g., timingpatterns to implement via control signals on control lines 191 andcontrol line 192, from processor unit 110.

As further illustrated in FIG. 1, the switches 141-144 are coupled torespective baseband converters 131-134 of a set 130 of basebandconverters. The baseband converters 131-134 may receive radio frequency(RF) signals from the output ports of the switches 141-144 and convertthe signals into baseband signals for processing by respective receivers121-124 in the set 120 of receivers. The receivers 121-124 may convertthe baseband signals into digital representations of the wireless testsignals that are received via the respective antenna sector units151-154. For instance, the receivers 121-124 may oversample the analogbaseband signals at a sampling interval under the control of timingsignals from a clock circuit 112 to create the digital representationsof the wireless test signals. Clock circuit 112, may comprise, forexample, a rubidium reference clock or the like.

The receivers 121-124 may output the digital representations of thewireless test signals to a processor unit 110 that is configured toperform various operations for determining measures of wireless channelparameters, as described herein. For instance, the processor unit 110may calculate, based upon the digital representations of the wirelesstest signals, a phase difference between wireless test signals receivedvia respective antennas. The processor unit 110 may further determine anangle of arrival (AoA) based upon the antenna positions and the phasedifference. In one example, the processor 110 may receive a referencecopy or copies of the wireless test signal(s), e.g., ZC sequences, fromthe transmitter. Accordingly, the processor 110 may determine acarrier-to-interference (CIR) ratio by comparing a ZC sequence receivedvia one of the antenna sector units 151-154 with a reference copy. Inone example, excess delay that is slightly less than the duration of theZC sequence can be measured. For instance, delay resolution of thedevice 100 may be approximately 0.6 to 1.3 nanoseconds, with a maximumexcess delay of 2.7 microseconds. Alternatively, or in addition, theprocessor unit 110 may calculate a path loss, an excess delay, a RMSdelay spread, a fade rate, a Doppler spread, a complex impulse response,or the like, from the digital representations of the wireless testsignals. In one example, the processor unit 110 may comprise all or aportion of a computing device or system, such as system 500, and/orprocessor 502 as described in connection with FIG. 5 below.

In one example, the processor unit 110 may perform further functions,including communicating with a transmitter-side device to coordinate thetiming of the transmission of the wireless test signals with activationsand deactivations of LNAs, the timing of control signals to switches141-144, to receive reference copies of wireless test signals that aretransmitted, and so forth. For instance, the processor unit 110 maymaintain a communication link, such a wired link, e.g., a severalhundred meter cable, or an out-of band wireless link (e.g., using adifferent set of antennas and a different RF communication band than theantennas of antenna sector units 151-154), or the like to communicatewith a device and/or a processor that is controlling the transmission ofthe wireless test signal via a transmitter-side antenna array. Theprocessor unit 110 may further provide instructions to timing controller115 based upon the information regarding the wireless test signals thatis received from the transmitter side. In other words, the controlsignals that timing controller 115 provides via control lines 191 andcontrol line 192 may be based upon the instructions received from theprocessor unit 110. In one example, the processor 110, the set 120 ofreceivers 121-124, and the set 130 of baseband converters 131-134 may bereferred to as a “receiver stage.” In one example, the receiver stagemay further include the clock circuit 112 and/or the timing controller115.

In addition, it should be noted that as used herein, the terms“configure” and “reconfigure” may refer to programming or loading acomputing device with computer-readable/computer-executableinstructions, code, and/or programs, e.g., in a memory, which whenexecuted by a processor of the computing device, may cause the computingdevice to perform various functions. Such terms may also encompassproviding variables, data values, tables, objects, or other datastructures or the like which may cause a computer device executingcomputer-readable instructions, code, and/or programs to functiondifferently depending upon the values of the variables or other datastructures that are provided.

It should also be noted that for ease of illustration, variouscomponents may be omitted from the example if FIG. 1, such as powersupply/voltage source(s) (e.g., +5V and/or −5V) for the processor unit110, the receivers 120, the LNAs of sector units 151-154, the set 140 ofswitches 141-144, and so forth. It should also be noted that variationsof the above device 100 may also be implemented in accordance with thepresent disclosure. For instance, in one example, antenna sector units151-154 may comprise two antennas per antenna sector unit, eightantennas per sector unit, and so forth. In another example, device 100may omit switches 141-144 and may instead comprise combiners, e.g., 4×1combiners. For instance, the device 100 may still activate one of theantenna sector units 151-154, while deactivating the others via controllines 191. Thus, only RF signals from antenna-LNA pairs of the activatedantenna sector unit should pass through the combiners to the set 130 ofbaseband converters 131-134. However, such an example may have anincreased noise penalty. For example, switches 141-144 implemented asPIN diode switches may have a noise figure of 8 dB of loss, whilecombiners may have a noise figure of 8 dB of loss or more, with lowerinput port isolation and therefore higher inter-sector interference. Inaddition, FIG. 1 illustrates processor unit 110, timing controller 115and timing circuit 112 as separate components. However, in anotherexample, these components may be integrated into a single unit. In stillanother example, functions of a component of device 100 may be deployedto multiple components. For instance, timing controller 115 may insteadcomprise separate components for sending switch control signals toswitches 141-144 and for sending LNA control signals to LNAs of antennasector units 151-154. Thus, various additional changes of a same or asimilar nature may be implemented in various devices in accordance withthe present disclosure.

FIG. 2 illustrates an example device 200, e.g., comprising at least aportion of a wireless channel sounder, in accordance with the presentdisclosure. For instance, device 200 may comprise a portion of thedevice 100 of FIG. 1, illustrated in greater detail. As illustrated inFIG. 2, antennas 221-224 are coupled to respective low-noise amplifiers(LNAs) 211-214. Thus, there are four antenna-LNA pairs. In one example,the antennas 221-224 include or are associated with respective feedhorns 231-234. In one example, antennas 221-224, LNAs 211-214, and feedhorns 231-234 may represent one of the antenna sector units 151-154 ofFIG. 1. As illustrated in FIG. 2, a timing controller 215 is coupled toLNAs 211-214 via a control line 295. In one example, the control line295 is one of a plurality of control lines 291 that controls LNAs ofdifferent antenna sector units. LNAs 211-214 are also powered via apower supply/voltage source 217 via power input lines 293. Asillustrated in FIG. 2, the output ports of the LNAs 211-214 are coupledto input ports of switches 241-244.

In one example, the LNAs 211-214 feed input ports of each of therespective switches 241-244. For instance, each of the switches 241-244may have four input ports, for receiving signals from four antennasector units. In addition, in one example, LNAs of a given antennasector unit will each be coupled to a respective input port of one ofthe switches 241-244 that is in a same assigned position. For instance,the input port positions of each switch 241-244 may be arrangedsequentially along one or more edges of the switch, where each of theswitches 241-244 is identical, or at least has a compatible input portarrangement. Alternatively, or in addition, the same input portpositions may indicate that respective input ports at different one ofthe switches 241-244 are addressable using a same switch control signalfrom timing controller 215 via control line 292. To illustrate, in theexample of FIG. 2, the LNAs 211-214 may be coupled to input ports in thethird position of each of the respective switches 241-244.

To further illustrate, switch 244 includes input ports 271-274. LNA 214is coupled to input port 273, e.g., the input port in the third positionat switch 244. Input port 271, e.g., the input port in the firstposition at switch 244, may be coupled to an LNA from a differentantenna sector unit (not shown). Similarly, input ports 273 and 274 maybe coupled to LNAs from still other antenna sector units, respectively.In one example, to select an antenna sector unit comprising antennas221-224 to receive wireless test signals, the timing controller 215 maygenerate an amplifier control signal on control line 295 to activateLNAs 211-214 (while suppressing or deactivating LNAs from other antennasector units via other control lines of the plurality of control lines291). Timing controller 215 may also send a switch control signal toswitches 241-244 via a control line 292 to cause switches 241-244 toselect input ports corresponding to the LNAs 211-214 that are associatedwith the antennas 221-224. For instance, the switch control signal oncontrol line 292 may cause switch 244 to select input port 273, andsimilarly with respect to the other switches 241-243. As such, switch244 may pass radio frequency (RF) signals received via input port 273from LNA 214 to the output port 284. Switches 241-243 may similarlyselect corresponding input ports and pass RF signals from thecorresponding input ports to the output ports 281-283 respectively.Output ports 281-284 may be further connected or coupled to respectivebaseband converters, such as baseband converters 131-134 of the device100 of FIG. 1.

When the receiving of the wireless test signals is completed for theantenna sector unit corresponding to antennas 221-224, the timingcontroller 215 may deactivate the LNAs 211-214 via control line 295 bysending another amplifier control signal, e.g., a disable signal, or byterminating the amplifier control signal that was used to activate theLNAs 211-213, and so forth. In addition, timing controller 215 may sendan amplifier control signal via another one of the plurality of controllines 291 to activate LNAs of a different antenna sector unit, and maysend another switch control signal to switches 241-244 via control line292 to cause switches 241-244 to select a different set of input portsto connect to the respective output ports 281-284, e.g., input portscorresponding to inputs from the antenna sector unit that is activated.Alternatively, or in addition, the timing controller 215 may send aswitch control signal to switches 241-244 to disable the switches, e.g.,if there are no more sectors to receive wireless test signals.

It should be noted that the example of FIG. 2 is just one example of aportion of a wireless channel sounder in accordance with the presentdisclosure, and that other, further and different configurations may beimplemented in additional examples. For instance, the timing controller215 may be configured via a processor or computing device, e.g., amanagement console or the like, in order to synchronize the activatingand deactivating of LNAs of different antenna sector units to thepattern of wireless test signals that are transmitted, e.g., on aper-sector, or per-antenna sector unit basis. In this regard, in oneexample, the timing controller 215 may be omitted as a separatecomponent and the control signals may be provided via a device and/orprocessor that is configured to perform various operations fordetermining measures of wireless channel parameters, such as processorunit 110 of FIG. 1. Furthermore, power supply/voltage source 217 isillustrated as powering LNAs 211-214 via power input lines 293. However,it should be understood that the same or a different powersupply/voltage source may also power switches 241-244. In still anotherexample, device 200 may implement more or less antennas in the portionof the device 200 that is illustrated in FIG. 2, e.g., two or moreantennas per sector/antenna sector unit. In addition, as mentionedabove, the device 100 of FIG. 1 may be modified to implement combinersin the place of switches 141-144. Similarly, switches 241-244 (and thecontrol line 292) may be omitted from the example of FIG. 2 and replacedwith passive N×1 combiners. Thus, these and other modifications are allcontemplated within the scope of the present disclosure.

FIG. 3 illustrates a perspective view of an example device 300, e.g., awireless channel sounder, in accordance with the present disclosure. Asillustrated in FIG. 3, the device 300 includes a plurality of antennasectors units 351-353 and 357-359. The device 300 may include additionalantenna sector units that are not visible in the view of FIG. 3. Thus,it should be understood that in one example, the device 300 may includea total of 16 sectors (and 64 antennas, in total). In one example, eachof the antenna sectors units 351-353 and 357-359 covers 45 degrees inazimuth and 45 degrees in elevation. For example, with respect toelevation beam coverage, antenna sectors unit 357 (and antenna sectorunits 358 and 359) cover from −22.5 degrees below horizon (305) to 22.5degrees above horizon (305) at half-power beamwidth, while antennasector unit 351 (and antenna sector units 352 and 353) cover from 22.5degrees above horizon (305) to 67.5 degrees above horizon (305) athalf-power beamwidth. With respect to azimuthal beam coverage, thedevice 300 may include two groups of eight sectors, e.g., an upper groupthat includes sectors 351-353 and five other sectors (not visible in theview of FIG. 3) and a lower group that includes sectors 357-359 and fiveother sectors (also not visible in the view of FIG. 3). With each sectorhaving a 45 degree half-power beamwidth, and where the beamwidths ofadjacent sectors are non-overlapping, the upper group and lower groupeach cover 360 degrees in azimuth.

Each of the antenna sector units of device 300 includes a plurality ofantennas, or antenna elements. For instance, the example of FIG. 3, eachof the antenna sectors units 351-353 and 357-359 includes four antennasarranged in a quad-array. To further illustrate, antenna sector unit 358includes feed horns 331-334 which feed four respective antenna-LNA pairs(not shown). The other antenna sectors units 351-353, 357 and 359 may besimilarly configured. It should be noted that in other examples, antennasector units may be deployed with different numbers of antennas, LNAs,and feed horns. For instance, in one example, an antenna sector unit inaccordance with the present disclosure may have at least two antennas(and hence at least two corresponding LNAs and at least twocorresponding feed horns).

In one example, antenna sectors units 351-353 and 357-359 (and theremaining antenna sector units of device 300 that are not visible inFIG. 3) may be activated and deactivated in a sequence. In one example,a transmitter may transmit wireless test signals via seven antennas of aswitched antenna array. In one example, the device 300 may receive 32samples of the wireless test signals from each antenna of the antennaarray of the transmitter at each antenna sector of device 300. Thus, forinstance, there may be 7×64 multiple input multiple output (MIMO)channels from which 32 samples may be obtained for each channel. Inaddition, in one example, the device 300 may have four receivers (notshown), e.g., arranged as illustrated in FIG. 1 and/or FIG. 2. Thus,measurements for wireless test signals from each transmitter antenna maybe taken on a per-sector basis, e.g., per quad array of the device 300.

It should be noted that the example of FIG. 3 is just one example of awireless channel sounder in accordance with the present disclosure, andthat other, further and different configurations may be implemented inadditional examples. For instance, more or less sectors having narroweror wider beamwidths may be used to cover 360 degrees in azimuth, sectorsmay be arranged to cover more or less range in elevation, more or lessantennas per sector may be deployed, a linear array or multiple lineararrays may be used instead of a quad array/square array, and so forth.

FIG. 4 illustrates a flowchart of an example method 400 for determiningmeasures of wireless channel parameters, in accordance with the presentdisclosure. In one example, steps, functions and/or operations of themethod 400 may be performed by a device as illustrated in FIG. 1 and/orFIG. 2, e.g., a wireless channel sounder, or any one or more componentsthereof, such as processor unit 110, or processor unit 110 inconjunction with timing controller 115 or timing controller 215,baseband converters 131-134, receivers 121-124, switches 141-144, LNAs211-214, and so forth. In one example, the steps, functions, oroperations of method 400 may be performed by a computing device orsystem 500, and/or processor 502 as described in connection with FIG. 5below. For instance, system 500 may represent a device, e.g., a wirelesschannel sounder, or a processor unit and/or other components of awireless channel sounder of the present disclosure. For illustrativepurposes, the method 400 is described in greater detail below inconnection with an example performed by a processor, such as processor502. The method 400 begins in step 405 and may proceed to optional step410 or to step 420.

At optional step 410, the processor receives timing information fortransmission of wireless signals from a transmitter, e.g., wireless testsignals for use in measuring one or more wireless channel parameters.For instance, the processor may receive the timing information fromanother processor, controller, or other device associated with thetransmitter. In one example, the transmitter may comprise a switchedarray with antennas having orientations where respective antenna beamscover respective portions of 120 degrees in azimuth with little to nooverlap at half power beamwidth. For instance, the array may compriseseven antennas, each with 18.5 degrees of half-power beamwidth to covera 120 degree (azimuthal) sector. Thus, in one example, the timinginformation may indicate a number of test signals to be transmitted fromeach antenna, a duration of the test signal(s), and so forth. In oneexample, additional information may be included with the timinginformation, such as a transmit power, information on transmitpolarization(s), reference copies of the wireless signals, and so forth.In one example, the timing information may relate to transmission of atleast a first plurality of wireless signals. In another example, thetiming information may relate to transmission of at least a firstplurality of wireless signals and a second plurality of wirelesssignals. In one example, the information received at optional step 410may be received out-of-band, e.g., via a wired connection between thetransmitter and a device of the processor.

At step 420, the processor activates a first plurality of low noiseamplifiers (LNAs) that are coupled to a first plurality of antennas. Forinstance, the processor may provide a control signal to turn on thefirst plurality of LNAs. In one example, the control signal may beprovided via a timing controller in communication with the processor,such as timing controller 115 of FIG. 1, or timing controller 215 ofFIG. 2. In addition, in one example, the activating of the firstplurality of LNAs may be synchronized to the transmission of the firstplurality of wireless signals, e.g., based upon the timing informationthat may be received at optional step 410.

At optional step 430, the processor provides a first control signal to aplurality of switches. For example, the first control signal causes eachof the plurality of switches to pass one of the first plurality ofwireless signals from a first of a plurality of input ports to an outputport of the respective switch. The switches may comprise switches141-144 of FIG. 1, or switches 241-244 of FIG. 2, for example. In oneexample, the control signal may be provided via a timing controller.

At step 440, the processor receives the first plurality of wirelesssignals via the first plurality of antennas and the first plurality ofLNAs. In particular, since the first plurality of LNAs are turned on andactivated, the wireless signals that are received via the firstplurality of antennas may be amplified and passed through the firstplurality of LNAs as radio frequency (RF) signals. In one example, theRF signals may further pass through the plurality of switches to aplurality of baseband converters and to a plurality of receivers todigitally sample baseband signals that are output by the basebandconverters. In particular, the switches may be arranged via the firstcontrol signal of optional step 430 to select respective input ports ofthe plurality of switches to pass the RF signals from the firstplurality of LNAs to the output ports of the respective switches. Inaddition, the baseband converters may convert the RF signals intobaseband signals, which may then be sampled at a given sampling rate tocreate digital representations of the first plurality of wirelesssignals.

At step 450, the processor determines a first measure of a wirelesschannel parameter based upon the first plurality of wireless signalsthat are received. For instance, the wireless channel parameters mayinclude: multipath direction(s) or angle(s) or arrival, acarrier-to-interference ratio, a path loss, a delay spread, a Dopplerspread, a fade rate, and so forth. To illustrate, with respect to angleof arrival (AoA), the processor may calculate, based upon the digitalrepresentations of the wireless signals, phase difference(s) betweenwireless signals received via respective antennas. The processor mayfurther determine an angle of arrival (AoA) based upon the antennapositions and the phase difference(s).

At step 460, the processor deactivates the first plurality of LNAs. Forexample, the processor may send a disable signal, terminating an enablesignal, etc. In one example, the deactivating may be provided via atiming controller. In addition, in one example, the deactivating thefirst plurality of LNAs may be synchronized to the transmission of thefirst plurality of wireless signals, e.g., based upon the timinginformation that may be received at optional step 410.

At step 470, the processor determines whether there are additionalsectors for which measurements are to be taken. If there are noadditional sectors, the method 400 may proceed to step 495 where themethod ends. However, if there are additional sectors, the steps 410-460may be repeated with respect to the additional sectors, or antennasector units, e.g., of a wireless channel sounder device of theprocessor, and/or with respect to additional antennas of a switchedantenna array of the transmitter. For example, the processor mayactivate a second plurality of LNAs that are coupled to a secondplurality of antennas at step 420, receive a second plurality ofwireless signals via the second plurality of antennas and the secondplurality of LNAs at step 440, determine a second measure of thewireless channel parameter based upon the second plurality of wirelesssignals that are received, at step 450, and deactivate the secondplurality of LNAs at step 460. At step 470, a determination may again bemade whether there are additional sectors for which measurements are tobe taken. If so, the steps 410-460 may continue to be repeated withrespect to additional sectors or antenna sector units, and/or withrespect to additional antennas of a switched antenna array of thetransmitter, e.g., for as many antenna sector unit—transmitter antennacombinations remain. If, however, there are no additional sectors, themethod 400 may proceed to step 495 where the method ends.

In addition, it should be noted that although not specificallyspecified, one or more steps, functions or operations of the method 400may include a storing, displaying and/or outputting step as required fora particular application. In other words, any data, records, fields,and/or intermediate results discussed in the method 400 can be stored,displayed and/or outputted to another device as required for aparticular application. Furthermore, steps or blocks in FIG. 4 thatrecite a determining operation or involve a decision do not necessarilyrequire that both branches of the determining operation be practiced. Inother words, one of the branches of the determining operation can bedeemed as an optional step. It should be noted that the method 400 maybe expanded to include additional steps. In addition, one or more steps,blocks, functions, or operations of the above described method 400 maycomprise optional steps, or can be combined, separated, and/or performedin a different order from that described above, without departing fromthe example embodiments of the present disclosure.

FIG. 5 depicts a high-level block diagram of a computing devicespecifically programmed to perform the functions described herein. Asdepicted in FIG. 5, the system 500 comprises one or more hardwareprocessor elements 502 (e.g., a central processing unit (CPU), amicroprocessor, or a multi-core processor), a memory 504 (e.g., randomaccess memory (RAM) and/or read only memory (ROM)), a module 505 fordetermining measures of wireless channel parameters, and variousinput/output devices 506 (e.g., storage devices, including but notlimited to, a tape drive, a floppy drive, a hard disk drive or a compactdisk drive, a receiver, a transmitter, a speaker, a display, a speechsynthesizer, an output port, an input port and a user input device (suchas a keyboard, a keypad, a mouse, a microphone and the like)). Althoughonly one processor element is shown, it should be noted that thecomputing device may employ a plurality of processor elements.Furthermore, although only one computing device is shown in the figure,if the method 400 as discussed above is implemented in a distributed orparallel manner for a particular illustrative example, i.e., the stepsof the above method 400, or the entire method 400 is implemented acrossmultiple or parallel computing device, then the computing device of thisfigure is intended to represent each of those multiple computingdevices.

Furthermore, one or more hardware processors can be utilized insupporting a virtualized or shared computing environment. Thevirtualized computing environment may support one or more virtualmachines representing computers, servers, or other computing devices. Insuch virtualized virtual machines, hardware components such as hardwareprocessors and computer-readable storage devices may be virtualized orlogically represented.

It should be noted that the present disclosure can be implemented insoftware and/or in a combination of software and hardware, e.g., usingapplication specific integrated circuits (ASIC), a programmable gatearray (PGA) including a Field PGA, or a state machine deployed on ahardware device, a computing device or any other hardware equivalents,e.g., computer readable instructions pertaining to the method discussedabove can be used to configure a hardware processor to perform thesteps, functions and/or operations of the above disclosed method 400. Inone embodiment, instructions and data for the present module or process505 for determining measures of wireless channel parameters (e.g., asoftware program comprising computer-executable instructions) can beloaded into memory 504 and executed by hardware processor element 502 toimplement the steps, functions or operations as discussed above inconnection with the illustrative method 400. Furthermore, when ahardware processor executes instructions to perform “operations,” thiscould include the hardware processor performing the operations directlyand/or facilitating, directing, or cooperating with another hardwaredevice or component (e.g., a co-processor and the like) to perform theoperations.

The processor executing the computer readable or software instructionsrelating to the above described method can be perceived as a programmedprocessor or a specialized processor. As such, the present module 505for determining measures of wireless channel parameters (includingassociated data structures) of the present disclosure can be stored on atangible or physical (broadly non-transitory) computer-readable storagedevice or medium, e.g., volatile memory, non-volatile memory, ROMmemory, RAM memory, magnetic or optical drive, device or diskette andthe like. Furthermore, a “tangible” computer-readable storage device ormedium comprises a physical device, a hardware device, or a device thatis discernible by the touch. More specifically, the computer-readablestorage device may comprise any physical devices that provide theability to store information such as data and/or instructions to beaccessed by a processor or a computing device such as a computer or anapplication server.

While various embodiments have been described above, it should beunderstood that they have been presented by way of example only, and nota limitation. Thus, the breadth and scope of a preferred embodimentshould not be limited by any of the above-described exemplaryembodiments, but should be defined only in accordance with the followingclaims and their equivalents.

What is claimed is:
 1. A method comprising: activating, by a processingsystem including at least one processor, a first plurality of low noiseamplifiers that is coupled to a first plurality of antennas; receiving,by the processing system from a transmitter, a first plurality ofwireless signals via the first plurality of antennas and the firstplurality of low noise amplifiers; determining, by the processingsystem, a first measure of a wireless channel parameter based upon thefirst plurality of wireless signals that is received; deactivating, bythe processing system, the first plurality of low noise amplifiers;activating, by the processing system, a second plurality of low noiseamplifiers that is coupled to a second plurality of antennas, whereinthe second plurality of antennas comprises different antennas from thefirst plurality of antennas; receiving, by the processing system fromthe transmitter, a second plurality of wireless signals via the secondplurality of antennas and the second plurality of low noise amplifiers;and determining, by the processing system, a second measure of thewireless channel parameter based upon the second plurality of wirelesssignals that is received.
 2. The method of claim 1, further comprising:receiving timing information for transmission of the first plurality ofwireless signals, wherein the activating of the first plurality of lownoise amplifiers and the deactivating of the first plurality of lownoise amplifiers are synchronized to the transmission of the firstplurality of wireless signals; and receiving timing information fortransmission of the second plurality of wireless signals, wherein theactivating of the second plurality of low noise amplifiers issynchronized to the transmission of the second plurality of wirelesssignals.
 3. The method of claim 1, further comprising: providing a firstcontrol signal to a plurality of switches, wherein the first controlsignal causes each of the plurality of switches to pass one of the firstplurality of wireless signals from a first port of a plurality of inputports to an output port.
 4. The method of claim 3, further comprising:providing a second control signal to the plurality of switches, whereinthe second control signal causes each of the plurality of switches topass one of the second plurality of wireless signals from a second portof the plurality of input ports to the output port.
 5. The method ofclaim 4, wherein the first control signal is synchronized to thetransmitting of the first plurality of wireless signals, and wherein thesecond control signal is synchronized to the transmitting of the secondplurality of wireless signals.
 6. The method of claim 1, wherein thefirst plurality of wireless signals and the second plurality of wirelesssignals comprise test signals for determining measures of the wirelesschannel parameter, the measures comprising the first measure and thesecond measure.
 7. An apparatus comprising: a processing systemincluding at least one processor; and a computer-readable medium storinginstructions which, when executed by the processing system, cause theprocessing system to perform operations, the operations comprising:activating a first plurality of low noise amplifiers that is coupled toa first plurality of antennas; receiving a first plurality of wirelesssignals from a transmitter via the first plurality of antennas and thefirst plurality of low noise amplifiers; determining a first measure ofa wireless channel parameter based upon the first plurality of wirelesssignals that is received; deactivating the first plurality of low noiseamplifiers; activating a second plurality of low noise amplifiers thatis coupled to a second plurality of antennas, wherein the secondplurality of antennas comprises different antennas from the firstplurality of antennas; receiving a second plurality of wireless signalsfrom the transmitter via the second plurality of antennas and the secondplurality of low noise amplifiers; and determining a second measure ofthe wireless channel parameter based upon the second plurality ofwireless signals that is received.
 8. The apparatus of claim 7, whereinthe operations further comprise: receiving timing information fortransmission of the first plurality of wireless signals, wherein theactivating of the first plurality of low noise amplifiers and thedeactivating of the first plurality of low noise amplifiers aresynchronized to the transmission of the first plurality of wirelesssignals; and receiving timing information for transmission of the secondplurality of wireless signals, wherein the activating of the secondplurality of low noise amplifiers is synchronized to the transmission ofthe second plurality of wireless signals.
 9. The apparatus of claim 7,wherein the operations further comprise: providing a first controlsignal to a plurality of switches, wherein the first control signalcauses each of the plurality of switches to pass one of the firstplurality of wireless signals from a first port of a plurality of inputports to an output port.
 10. The apparatus of claim 9, wherein theoperations further comprise: providing a second control signal to theplurality of switches, wherein the second control signal causes each ofthe plurality of switches to pass one of the second plurality ofwireless signals from a second port of the plurality of input ports tothe output port.
 11. The apparatus of claim 10, wherein the firstcontrol signal is synchronized to the transmitting of the firstplurality of wireless signals, and wherein the second control signal issynchronized to the transmitting of the second plurality of wirelesssignals.
 12. The apparatus of claim 7, wherein the first plurality ofwireless signals and the second plurality of wireless signals comprisetest signals for determining measures of the wireless channel parameter,the measures comprising the first measure and the second measure. 13.The apparatus of claim 7, wherein the first plurality of low noiseamplifiers and the first plurality of antennas are arranged into one ormore sectors.
 14. A non-transitory computer-readable medium storinginstructions which, when executed by a processing system including atleast one processor, cause the processing system to perform operations,the operations comprising: activating a first plurality of low noiseamplifiers that is coupled to a first plurality of antennas; receiving afirst plurality of wireless signals from a transmitter via the firstplurality of antennas and the first plurality of low noise amplifiers;determining a first measure of a wireless channel parameter based uponthe first plurality of wireless signals that is received; deactivatingthe first plurality of low noise amplifiers; activating a secondplurality of low noise amplifiers that is coupled to a second pluralityof antennas, wherein the second plurality of antennas comprisesdifferent antennas from the first plurality of antennas; receiving asecond plurality of wireless signals from the transmitter via the secondplurality of antennas and the second plurality of low noise amplifiers;and determining a second measure of the wireless channel parameter basedupon the second plurality of wireless signals that is received.
 15. Thenon-transitory computer-readable medium of claim 14, wherein theoperations further comprise: receiving timing information fortransmission of the first plurality of wireless signals, wherein theactivating of the first plurality of low noise amplifiers and thedeactivating of the first plurality of low noise amplifiers aresynchronized to the transmission of the first plurality of wirelesssignals; and receiving timing information for transmission of the secondplurality of wireless signals, wherein the activating of the secondplurality of low noise amplifiers is synchronized to the transmission ofthe second plurality of wireless signals.
 16. The non-transitorycomputer-readable medium of claim 14, wherein the operations furthercomprise: providing a first control signal to a plurality of switches,wherein the first control signal causes each of the plurality ofswitches to pass one of the first plurality of wireless signals from afirst port of a plurality of input ports to an output port.
 17. Thenon-transitory computer-readable medium of claim 16, wherein theoperations further comprise: providing a second control signal to theplurality of switches, wherein the second control signal causes each ofthe plurality of switches to pass one of the second plurality ofwireless signals from a second port of the plurality of input ports tothe output port.
 18. The non-transitory computer-readable medium ofclaim 17, wherein the first control signal is synchronized to thetransmitting of the first plurality of wireless signals, and wherein thesecond control signal is synchronized to the transmitting of the secondplurality of wireless signals.
 19. The non-transitory computer-readablemedium of claim 14, wherein the first plurality of wireless signals andthe second plurality of wireless signals comprise test signals fordetermining measures of the wireless channel parameter, the measurescomprising the first measure and the second measure.
 20. Thenon-transitory computer-readable medium of claim 14, wherein the firstplurality of low noise amplifiers and the first plurality of antennasare arranged into one or more sectors.